The present invention relates to a power system for supplying electrical power to a load, and more specifically to a power system having a plurality of DC power sources and which can be readily reconfigured to meet the changing power requirements of the load or changes in the performance characteristics of the respective DC power sources.
A fuel cell is a device which can readily convert chemical energy to electrical energy by the reaction of a fuel gas with a suitable oxidant supply. In a proton exchange membrane fuel cell, for example, the fuel gas is typically hydrogen and the oxidant supply comprises oxygen (or more typically ambient air). In fuel cells of this type a membrane electrode diffusion assembly is provided and which includes a solid polymer electrolyte which has opposite anode and cathode sides. Appropriate catalysts are deposited on the opposite anode and cathode sides. During operation, the fuel gas reacts with a catalyst on the anode side to produce hydrogen ions which migrate through the solid polymer electrolyte to the opposite cathode side. Meanwhile, the oxidant supply introduced to the cathode side is present to react with the hydrogen ions in the presence of the catalyst to produce water and a resulting electrical output.
Many fuel cell designs have been provided through the years, and much research and development activity has been conducted to develop a fuel cell which meets the perceived performance and cost per watt requirements of various users. Despite decades of research, fuel cells have not been widely embraced except for narrow commercial applications. While many designs have emerged, and which have operated with various degrees of success, shortcomings in some peculiar aspect of their individual designs have resulted in difficulties which have detracted from their widespread commercial acceptance and perceived usefulness. In this regard, one of the primary shortcomings with most fuel cell designs is reliability and the lack of ability to serve a load if part of the fuel cell fails or declines in performance.
For example, one of the byproducts of fuel cell operation is heat. While some degree of heat is necessary, and even desirable, to allow the fuel cell to reach its maximum power output, too much heat can cause catastrophic failure of the same fuel cell. Further, and as noted above, another byproduct of fuel cell operation is water. Similarly with this byproduct, some water is desirable to facilitate the movement of hydrogen ions across the proton exchange membrane. However, too much water can cause the fuel cell to xe2x80x9cflood outxe2x80x9d resulting in the further failure. These and other types of problems can result in partial or total loss of electrical output from a portion of the fuel cell system. As a general matter in most fuel cell systems, these problems can lead to a total shutdown of the fuel cell system and the inability of the fuel cell system to serve the load in any manner. This perceived inability to serve the load notwithstanding, performance problems which may arise from time to time with individual membranes or other assemblies has seriously impeded the widespread commercial introduction and utilization of fuel cells.
Yet a further limitation in earlier fuel cell designs has long been recognized, that being, earlier fuel cell designs have on the one hand not readily scaled down to specific load applications, and on the other hand, if a failure of the fuel cell has occurred it has been difficult to address same without disconnecting the fuel cell from the load. This is undesirable, of course, in some applications where uninterruptible power requirements for critical operations such as telecommunications, navigational aides and critical computer operations mandate such types of power be provided. These and other perceived shortcomings are addressed by means of the present invention.
Therefore, one aspect of the present invention is to provide a power system for supplying power to a load which includes a plurality of DC power sources and which include at least one fuel cell which provides power to the load; and a control electronics assembly electronically coupled to the respective DC power sources and which selectively reconfigures the plurality of DC power sources to substantially serve the power requirements of the load.
Another aspect of the present invention is to provide a power system for servicing the power requirements of a load and which includes a plurality of DC power sources having predetermined operational parameters and which includes at least one fuel cell, and wherein at least one of the DC power sources has discrete portions which may be operably bypassed while any remaining portions simultaneously continue operating; and a control electronics assembly electrically coupled in voltage sensing and controlling relation relative to the respective DC power sources or portions thereof, and which upon sensing a predetermined operational condition of the plurality of DC power sources or portions thereof and/or a change in the power requirements of the load, selectively reconfigures the plurality of DC power sources or portions thereof to substantially serve the power requirements of the load.
Still a further aspect of the present invention relates to a power system for servicing the power requirements of a load and which includes a plurality of DC power sources, at least one of which is a fuel cell, and at least one of which is a charge storage device, and wherein each of the DC power sources have predetermined operational parameters, and wherein the at least one fuel cell has discrete portions which may be individually rendered inoperable while the remaining portions continue in operation, and wherein the respective DC power sources are selectively electrically coupled in electrical power delivering relation relative to the load; and a control electronics assembly is controllably coupled with each of the DC power sources and further coupled in sensing relation relative to the power requirements of the load, and the predetermined performance parameters of the respective DC power sources, and wherein the control electronics assembly reconfigures the plurality of DC power sources to meet the power requirements of the load.
Another aspect of the present invention relates to a power system which includes a plurality of DC power sources, which include at least one fuel cell, and wherein the DC sources ultimately serve as the source of power being supplied to the load. Other DC power sources which may be employed include fuel cell stacks. The power system further has a control electronics assembly coupled to each of the respective power sources. The control electronics assembly serves to collectively reconfigure, and couple, the plurality of DC power sources, by way of corresponding control elements, that is, solid state or electromechanical switches, to supply the power requirements of the load.
Another aspect of the present invention relates to a power system which has charge storage devices which typically comprise storage batteries and/or ultra-capacitors. Control electronics are provided to coordinate charging and discharging of the charge storage devices by way of corresponding control elements. Various DC power sources provide storage charging power. Discharging of the respective storage devices is performed to serve the power requirement of the load. The control electronics which are provided further include sensing ability to monitor such operating conditions as voltage and/or current of the DC power sources, charge storage devices, and the load. Other sensing may be incorporated as required. Other control elements may include valves for supplying fuel or oxidant when fuel cells are employed.
Another aspect of the present invention relates to control strategies which permit selective reconfiguration of available DC power sources. These control strategies may be automatically executed by way of a control electronics assembly and other control elements as a result of sensing predetermined operating conditions. This control strategy arrangement makes it possible for a portion, or entire fuel cells to be removed from service or electrically or physically bypassed while other DC power sources and/or charge storage devices continue to substantially supply the power requirements of the load.
Still another aspect of the present invention relates to a power system which substantially supplies the power requirements of a load, and wherein the power system has a plurality of DC power sources, and wherein at least one of which is an ion exchange fuel cell module. Each ion exchange fuel cell module produces heat energy during operation. Further a bifurcated air flow is provided to dissipate the heat energy typically to the ambient environment. Other DC power sources may comprise individual fuel cells and fuel cell stacks in combination with the fuel cell module.
Another aspect of the present invention relates to a power system which includes charge storage devices such as; storage batteries; and ultracapacitors. In this arrangement control electronics and control elements are provided which selectively couple and decouple each of these DC power sources and the load, into various circuit configurations. This electrical switching arrangement allows a substantially constant supply of power to the load. Additionally, a control electronics assembly is provided and which has a sensing ability for monitoring the operating conditions of each of the DC power sources.
Another aspect of the present invention relates to control elements which provide for the effective delivery of fuel and air to individual fuel cell modules or stacks, and the electrical coupling and decoupling of system devices, that is other DC power sources, to the accompanying load.
Still another aspect of the present invention relates to electrical bypassing or shunting of fuel cell modules or stacks through the manipulation of switch-type control elements. This electrical bypassing or shunting facilitates the shutdown; servicing; replacement and/or startup of individual DC power sources or storage devices while the remaining DC power sources substantially supply the power requirements of the load. Appropriate operator interface is provided which allows for adjustment of shunting cycles (as needed); manual override; and monitoring of various operating conditions.
Still another aspect of the present invention relates to control electronics and control elements which permit the generation of AC power to be supplied to a load. This is achieved through the synchronized, cyclic coupling and decoupling of individual DC power sources in a series circuit arrangement so as to approximate a sine-wave power signal that is then coupled to the load. In the event that the power requirement is dynamic in nature (changing over time) the voltage of the resulting alternating current power may be varied through the addition or subtraction from the number of individual DC power sources and/or storage elements which are coupled to the load during any particular phase of the generating cycle.
Another aspect of the present invention relates to a power system which substantially supplies the power requirements of a load and which includes a plurality of different DC power sources such as fuel cell stacks; ion exchange fuel cell modules; segmented fuel cells; photovoltaic panels; wind generation; hydro-generation; storage batteries and/or ultracapacitors.
Yet a further aspect of the present invention relates to a control electronics assembly having corresponding control elements and sensing ability which is configured for the measurement of system operating conditions, that is voltage; current; temperature; and other operating parameters of both the respective DC power sources and the load. Operator interface is provided for the control electronics and which permits human interrogation of system operating conditions and adjustment of control strategies, as well as override; startup; and shutdown capabilities both locally and remotely.
Another aspect of the present invention relates to a memory provided with the control electronics assembly and which provides for the automated operation of the power system based upon predetermined operational conditions stored within such memory. In this regard, should the voltage of a DC power source, such as that provided by a particular fuel cell segment decay to a predetermined value, the control electronics assembly and corresponding control elements may react appropriately by electrically shunting, or bypassing that particular segment; curtail the fuel and/or air supply to the affected fuel cell segment; and/or alert a human operator by way of an operator interface to the conditions so that appropriate corrective action may be provided.
These and other aspects of the present invention will be discussed in further detail hereinafter.